前言
RTC
RTC 即实时时钟（Real-Time Clock），主要是功能有：
- 时间保持：RTC可以在断电的时候，仍然保持计时功能，保证时间的连续性
- 时间显示与设置：RTC可以向系统提供年、月、日、时、分、秒等信息，系统也可以通过接口校准RTC的时间保证准确性
关机闹钟PowerOffAlarm
PowerOffAlarm 是一个与安卓系统关机闹钟功能相关的应用或组件。
当用户设置好关机闹钟后，会向 PowerOffAlarm 发送设定关机闹钟广播并传入闹钟时间参数，PowerOffAlarm 接收到广播后，根据预设提前开机时间和闹钟时间往实时时钟（RTC）中写入时间，并将该时间写入文件中暂存
需要注意的是，PowerOffAlarm 中使用的时间默认是当前时区的时间，若传入的时间戳是其他时区的，则需要调整为当前时区的时间戳
时区
时区是为了适应地球自转造成的不同地区时间差异而划分的区域。
正文
源码分析
关机闹钟 PowerOffAlarm 源码路径：vendor/qcom/proprietary/PowerOffAlarm/src/com/qualcomm/qti/poweroffalarm
首先查看 AndroidManifest.xml 中与关机闹钟相关的广播接收器的源代码：
<receiver android:name=".PowerOffAlarmBroadcastReceiver" android:permission="org.codeaurora.permission.POWER_OFF_ALARM" android:exported="true" android:directBootAware="true" android:label="PowerOffAlarmBroadcastReceiver"> <intent-filter android:priority="1000"> <!-- 取消闹钟的广播 --> <action android:name="org.codeaurora.poweroffalarm.action.CANCEL_ALARM" /> <!-- 设置闹钟的广播 --> <action android:name="org.codeaurora.poweroffalarm.action.SET_ALARM" /> <action android:name="android.intent.action.LOCKED_BOOT_COMPLETED" /> </intent-filter> </receiver> <receiver android:name="com.qualcomm.qti.poweroffalarm.PowerOffAlarmDialog$ShutDownReceiver" android:permission="org.codeaurora.permission.POWER_OFF_ALARM"> <intent-filter> <!-- 关机广播 --> <action android:name="org.codeaurora.poweroffalarm.action.ALARM_POWER_OFF"/> </intent-filter> </receiver> 对于设置关机闹钟和取消关机闹钟的逻辑，跟踪到 PowerOffAlarmBroadcastReceiver 的源代码：vendorqcomproprietaryPowerOffAlarmsrccomqualcommqtipoweroffalarmPowerOffAlarmBroadcastReceiver.java
/******************************************************************************* @file PowerOffAlarmBroadcastReceiver.java @brief Receive "org.codeaurora.poweroffalarm.action.SET_ALARM" action to set power off alarm and receive "org.codeaurora.poweroffalarm.action.CANCEL_ALARM" action to cancel alarm. ******************************************************************************/ public class PowerOffAlarmBroadcastReceiver extends BroadcastReceiver { //设置关机闹钟的动作 private static final String ACTION_SET_POWEROFF_ALARM = "org.codeaurora.poweroffalarm.action.SET_ALARM"; //设置取消关机闹钟的动作 private static final String ACTION_CANCEL_POWEROFF_ALARM = "org.codeaurora.poweroffalarm.action.CANCEL_ALARM"; //设置关机闹钟的意图携带的 extra 的 key private static final String TIME = "time"; //设置或取消闹钟 if (ACTION_SET_POWEROFF_ALARM.equals(action)) {//设置闹钟动作 long alarmTime = intent.getLongExtra(TIME, PowerOffAlarmUtils.DEFAULT_ALARM_TIME);//取出要设置的时间戳 long alarmInPref = PowerOffAlarmUtils.getAlarmFromPreference(context);//获取之前设置的时间戳 Log.d(TAG, "Set power off alarm : alarm time " + alarmTime + " time in pref " + alarmInPref); PowerOffAlarmUtils.saveAlarmToPreference(context, alarmTime);//保存新的时间戳 long alarmTimeToRtc = PowerOffAlarmUtils.setAlarmToRtc(alarmTime);//转化为 RTC 的时间 if (alarmTimeToRtc != FAILURE) {//是个合法时间 persistData.setAlarmTime(alarmTime); persistData.setAlarmStatus(PowerOffAlarmUtils.ALARM_STATUS_TO_FIRE); persistData.setSnoozeTime(PowerOffAlarmUtils.DEFAULT_ALARM_TIME); persistData.writeDataToFile();//会把设置的 RTC 时间存在文件里面 PowerOffAlarmUtils.saveRtcAlarmToPreference(context, alarmTimeToRtc); } } else if (ACTION_CANCEL_POWEROFF_ALARM.equals(action)){//取消闹钟动作 long alarmTime = intent.getLongExtra(TIME, PowerOffAlarmUtils.DEFAULT_ALARM_TIME);//获取要取消的闹钟时间戳 long alarmInPref = PowerOffAlarmUtils.getAlarmFromPreference(context);//获取之前设置的时间戳 if (alarmTime == alarmInPref) {//与之前设置的时间戳相同，那就可以取消设置的闹钟 PowerOffAlarmUtils.saveAlarmToPreference(context, PowerOffAlarmUtils.DEFAULT_ALARM_TIME); PowerOffAlarmUtils.saveRtcAlarmToPreference(context, PowerOffAlarmUtils.DEFAULT_ALARM_TIME); int rtc = PowerOffAlarmUtils.cancelAlarmInRtc(); if (rtc < 0) { Log.d(TAG, "Cancel alarm time in rtc failed "); } persistData.setAlarmStatus(PowerOffAlarmUtils.ALARM_STATUS_NONE); persistData.setSnoozeTime(PowerOffAlarmUtils.DEFAULT_ALARM_TIME); persistData.setAlarmTime(PowerOffAlarmUtils.DEFAULT_ALARM_TIME); persistData.writeDataToFile(); } } } 最后追踪到 PowerOffAlarmUtils 的源代码：vendorqcomproprietaryPowerOffAlarmsrccomqualcommqtipoweroffalarmPowerOffAlarmUtils.java
/** * Set alarm time to rtc register * * @param time alarm time based on current time (ms) * @return set result -- Fail, return FAILURE; Success, * return the alarm time to rtc */ public static final long MS_IN_ONE_MIN = 60000L;//一分钟 private static final long SEC_TO_MS = 1000L;//将秒转化为毫秒 public static long setAlarmToRtc(long alarmTime/*未来时间的时间戳*/) { long currentTime = System.currentTimeMillis();//当前时间的时间戳 long alarmInRtc = getAlarmFromRtc(); long rtcTime = getRtcTime(); // MS_IN_ONE_MIN 是系统预留的开机时间 long timeDelta = alarmTime - currentTime - MS_IN_ONE_MIN;//获取当前到未来的时间戳的差值（单位：ms） // alarm in two minute is not supported if (timeDelta <= 0) { Log.d(TAG, "setAlarmToRtc failed: alarm time is in one minute"); return FAILURE;//设置的时间若过短就返回失败 } long alarmTimeToRtc = timeDelta / SEC_TO_MS + rtcTime;//计算出要唤醒机器的 RTC 时间（单位：ms） try { IAlarm mProxy = IAlarm.getService(); int ret = mProxy.setAlarm(alarmTimeToRtc);//设置 RTC 时间 if (ret == SUCCESS) {//设置成功 return alarmTimeToRtc; } else { return FAILURE;//设置失败 } } catch (Exception e) { Log.d(TAG, e.toString()); return FAILURE; } } 对于关机广播的源代码，首先追踪到源代码：vendorqcomproprietaryPowerOffAlarmsrccomqualcommqtipoweroffalarm.java
public class PowerOffAlarmDialog extends Activity{ public static class ShutDownReceiver extends BroadcastReceiver { @Override public void onReceive(final Context context, Intent intent) { PowerOffAlarmUtils.powerOff(context);//关机 } } } 随后追踪到 PowerOffAlarmUtils.java 中：
private static final String ACTION_REQUEST_SHUTDOWN = "com.android.internal.intent.action.REQUEST_SHUTDOWN"; public static void powerOff(Context context) { //想要直接使用这个函数的话，app必须是系统app，且具有如下权限： //<uses-permission android:name="android.permission.SHUTDOWN"/> Intent requestShutdown = new Intent(ACTION_REQUEST_SHUTDOWN); requestShutdown.putExtra(EXTRA_KEY_CONFIRM, false);//true 是弹窗询问，false 是不弹窗直接关机 requestShutdown.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); context.startActivity(requestShutdown); } 项目实战
设置关机闹钟
public static final String POWER_OFF_ALARM_PACKAGE = "com.qualcomm.qti.poweroffalarm"; private static final long MS_IN_ONE_MIN = 6000L; /** * 设置关机闹钟，在到达预定的时间戳时开机 * * @param mContext 上下文 * @param millis 未来的时间戳 */ public static void startPowerOnAlarm(Context mContext, long millis) {//开机 Intent intent = new Intent(Constants.ACTION_SET_POWEROFF_ALARM); intent.addFlags(Intent.FLAG_RECEIVER_FOREGROUND); intent.setPackage(POWER_OFF_ALARM_PACKAGE); long time = millis + MS_IN_ONE_MIN; intent.putExtra("time", time); mContext.sendBroadcast(intent); } 取消关机闹钟
public static final String ACTION_CANCEL_POWEROFF_ALARM = "org.codeaurora.poweroffalarm.action.CANCEL_ALARM"; /** * 取消关机闹钟，取消设定在时间戳 millis 的闹钟 * * @param mContext 上下文 * @param millis 取消的闹钟时间戳 */ public static void cancelAlarm(Context mContext, long millis) { Intent intent = new Intent(ACTION_CANCEL_POWEROFF_ALARM); intent.addFlags(Intent.FLAG_RECEIVER_FOREGROUND); intent.setPackage(POWER_OFF_ALARM_PACKAGE); millis += MS_IN_ONE_MIN; intent.putExtra("time", millis); sendBroadcast(intent); } 关机功能
public static void startShutDown(Context mContext) {//关机 Intent intent = new Intent("org.codeaurora.poweroffalarm.action.ALARM_POWER_OFF"); intent.setPackage(POWER_OFF_ALARM_PACKAGE); intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); mContext.sendBroadcast(intent); //也可以使用如下代码实现，但必须是系统应用且带有如下权限: // <uses-permission android:name="android.permission.SHUTDOWN"/> // String action = "com.android.internal.intent.action.REQUEST_SHUTDOWN"; // if(Build.VERSION.SDK_INT <= Build.VERSION_CODES.N){ // action = "android.intent.action.ACTION_REQUEST_SHUTDOWN"; // } // Intent intent = new Intent(action); // intent.putExtra("android.intent.extra.KEY_CONFIRM", false); // intent.setFlags(Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS); // intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); // mContext.startActivity(intent); } 
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